MAF method
/ mæf ˈmɛθ.əd / · proper noun
Also: Maffetone method, Maximum Aerobic Function, MAF training, 180 formula
An aerobic-base building methodology developed by Dr. Phil Maffetone in the 1980s, centered on training at a heart rate ceiling calculated as 180 minus age, with adjustments for individual fitness and health history. The method aims to develop fat oxidation, mitochondrial density, and capillarization without crossing into glycolytic stress.
The 180 formula
- Base value: 180 − age in years
- Subtract 10: if recovering from major illness or injury, or on regular medication
- Subtract 5: if injured frequently, often sick, or training inconsistently
- No adjustment: if training consistently for 1-2 years without injury
- Add 5: if training competitively for 2+ years with progress and no injury
Example: a 35-year-old athlete with consistent training would target 145 bpm as their MAF ceiling. A 35-year-old recovering from injury would target 135 bpm.
Core principle
Below the MAF heart rate, the body relies primarily on fat oxidation and the aerobic energy system. Training exclusively below MAF for an extended period (often 3-6 months in the "MAF base" phase) develops aerobic enzymes, mitochondria, and capillary density without the cortisol load of high-intensity work. The hypothesis: building a deep aerobic base raises the ceiling for all intensities later.
The MAF test
Run or bike at MAF heart rate over a fixed distance (e.g., 5K or 5 miles) at the same time of day and same conditions, monthly. Pace at the same heart rate should improve as aerobic capacity grows. A plateauing or worsening MAF test signals overtraining or insufficient recovery.
Strengths
- Injury prevention: exclusively low-intensity work has very low injury risk.
- Fat-burning adaptation: athletes routinely improve their substrate utilization, racing more efficiently in events lasting 90+ minutes.
- Sustainable: can be done year-round without burnout.
- Self-corrects: the heart rate ceiling adjusts intensity automatically to current fitness and stress.
Critiques and limits
- The formula is heuristic, not validated: 180 − age is not derived from physiological measurement. For some athletes it sits well below their actual LT1; for others it overshoots.
- Plateau without intensity: in trained athletes, exclusively-low-intensity work eventually stops driving adaptation. Most successful applications combine MAF base periods with later intensity blocks.
- Slow: many athletes report 3-6 months of plodding before pace at MAF improves meaningfully: psychologically difficult.
For hybrid athletes
The MAF method is broadly compatible with the polarized training model (both prioritize Z2 volume) but MAF is more rigid in capping intensity. Many HYROX-focused hybrid athletes use a 6-8 week MAF base before adding race-specific intervals in the final block. The benefit: a deeper aerobic ceiling that supports the 60-90 minute race effort. The cost: short-term intensity decay if applied for too long.